Distillation



Aug. 24, 1943. p LAMBERT 2,327,534

DISTILLATION Filed July A14, 1939 Fi www@ (aghi 'ompamswt-sj PierreLambert Patented 24, l

Y The Lumm-us Oom-Paay, New

lcorporation of Berlaware ,Appiieatipig Jmyjigi, 1.939,1 serie; No;@34h30 This inventioh relates to improvements iiifi'liief offi'aetioriailydistilling vcomplex liqiiid In theA distillation ofeompexf hydrocarbon mixtures,V such aspetrolewm-s, topped mildes, andthe like, :semaftion of the iight'irom the heayier components isordinarily accomplished inaldis column equipped Jvrititr-Iriea ns for`reboil.-

ing Voir,.strippingV the bottoms jthereifromwith steam. Howeileiyit isnot always possible to at# tain the desired separation in such a system,esonciaiyiithe heavier @imponente 'are greater in ammmt than the .lightcomponents, because of the diieaiity enooiimtered in .,egconomic'ailystripping ail of iight components from .the .heat/ier eem-l pohemtsinthe striiiphigasecbion ofthe disti'l'a- .tioncofllmf n; I

AS im `mammie ef sueh-dimenmyixit is known that theVifaptmslri'ilig.from ,stripiihg section past thefeed plate or feedchamber in .a A distiiiation column carry a ipfo'rtion of `the heaviercombatiente of the ieedilnto xectifyingsectioi-L whiieh heavylooniinonehts faire returned to' the f section by. mees the Tefiux fromthe plates above theieedy Since any iight oompoments which maybepresentinlthe ifeugrmust be stripping section 'is there'by increased.Moreover,

when the natureefthe reed is seeiithetthe liquid, portion isconsiderably'heavierjtlianthe -reilux Coming' from the 4 plates aboife",the feed ,has jar;

A the Qeoihppiierits 'reglarge in amountas pomparedto Vthe ',iightcomponents',

vahiout ofY utiiities heeded toT eifectdthelspara e Af fumier object 6ithe ifyeritiehiis t moi/ide a method.oifdistillingy"a hydpooarhoh Inixtur'e. containing a s ihall'famolht Lof iight components the.stripping ture'fthe he subjected toy: Wiffleeiltdefieer .t

e. A is eliminate@ qurther `objets an@ a preferred form of embodiment ofthe stribped olii:"after theV refi'iixhasmixedwith the Ieedplaiei'gid;the tota1 Stripping duty in the a greater v.of Stripgiiagsteam must heiisedV v m ehe r'serimaine' sections for musi sumlieii. ii the hea-ifs'components are -suhiected to reboiiingrto insure eomplete separatiohfof,they iight :trom'thehea'vy vomito:freiits.-2 ,Use iG-fxeXQeS- v sivequantities sii-stripping steam isohiectiom 5 able for reaismxisoeconomyrwhereasaise .oiaddi, tional heat ltoi the temperature .Ggf me loilirigA is `riot .onlyuexperisivemutmayhe entirelyfirnprao -f tiabiebeczms'eiof'the tendones( ef the heavy. eomundergo ci'iaekimg'arieastiohs heated to temperatures much above' 700?.

The prinevpaiobieet oiitheprsentinvemtionis i `iri'ixtuijesbyfmeansofwhiohit is possible'fto' shafrpiy separate the iightiroinfthe' heavir` compiments Itherein,*leilifthf-a material `rehiotiorii iii the Y vbeine. returned 150th dr illustrativethereofQ-irilwhich: n

ra. gement ,for caivrying out the lpreseiit Fig. 3 'is an alternativeflots?` arrahgeiientoi thatshQwnaFi-az; Y.

e present ini/enti@ icdniempletes: the sharp,

' seiaifationyoi the lishtfgooirijporients froiiila hydrocarbon mixturebythe withdrawal .of the .eri-

lthe Agooint,foizreiiux l thdrawa1, and theffheavy componer-its .t being:combined `withV the` bot-toms. `lfimnfthe distillation comin-nto formaresiduum `trom ming-ling with the l-heavy Components strippnggseotion ofthe distillatio'if` `co1- lstrippi-ng 4tlrieieiux inya separate j Quemasharper sepaifaiziori ofthe lightfromthe" .1 daietionih .theamountrofutilitiesneessary, In` addiiinmetheleoiencyfofairactionatiohisdn-L 'eeantegfa ff Y tion Wili heapparent .fromthe following dSGlDf Vetioii takeh-in connection with the attae'ijiedr .L 1 isaydiag-rammaticView; of a preierised.

, agrairnhatic VViUeW-foi a modified ow-arrahgemehtgg? The entirelreiiux is withdrawn from thev bottom of the rectiying Zone -and isstripped independently of the `ilashing operation. Employment of Vaflash Vdistillation is particularly useful when vthe heavycomponents'are of lsucha character that they can not 'be subjected tohigh temperatures of reboiling without dangerA of cracking.`

I have alsofound the present invention to be I am able to accomplish theseparation of a tower especially useful when corrosive materials', oc-

duction in the overall amount of utilities required` for the separation.

v. steam or heat for reboiling`V is necessary in tower curring in thelower boiling range of. the heavy components are present in the'material'to be separated. By stripping the reflux independently, wherebythe corrosive materials are concentrated inthe bottomsl from the refluxstripper, I amable to avoid the corrosion diiculties whichwould. w

.otherwiseqbe' encountered in reboiling Yofthe heavy components.

. In accordance with@J preierredformof em# 'bodiment of'm'yin'vention;as shown in Fig. 1, a hydrocarbon mixture, such as acrude petroleum or atopped crude, 4.suitably preheatedyis fedto fractionating' tower` Iii atI2. Althoughmany types ofV hydrocarbon mixtures 4may 'be fractionatedr'by ymeans o'f v my invention, itv is especially adaptable tomixturescontaining ailarge amount of heavy components anda smallgamount of'light components. Tower Iii is a typical distillanon coiump, lcontaining bubme plates, suitable v for''fractionation of liquidmixturesz.

isjof ,such a nature, however, that it is subject to decomposition atthe reboiling'temperature regnired,' stripping steammay be introduced atI6. .l

The vapors from 'I4 and the feed yapors',rising through vapor passage I8into the rectifying sectionj2, entrain a portion ofthe heavy componentsof the feed'. 'These heavy components arev absorbed by reux liquid,which is conveniently introducedatZI, In the lower portionolvtherectifying section 20, this reux contains 'a' con-y f siderable'proportion of light components',-which wouldnormally be carriedinto thestripping sec-Y tion I4 yif the reiiux were allowed to mix'with theincoming feed.` i

In .accordance with my inventionr-fthis 're'ilux'V l isfcollected'fonplate 22, which contair'is vapor passage v I8 butwhich`hasno A'liquiddownow line Mland tfed tohstrippingc olurnr'i 25; inwhich `the-light components'are stripped out,fas by use ofjreboiler 3Sor stripping steam introduced at 28. T hese light components arelreturnedto `tower I Il atia' suitable point'abovetherefluxwithdrawalby'line 30. The Abottoms from the strip ping column Y2B,consisting mostly of-'the lighter portion. of the heavy' components,l isremoved at 212.V Sincefthe1 bottoms 'from stripperfZ areadjacentin'l'character-to thebottorns "removed at fffrom tower I0,thetwo Abottornsfstreams may bcombined 'to iormf'a residualproductfreeoflight compon'entsgv'he light components arere pipes; L' .The totalreux is'then drawn oitthrough'v Vr'eilux'are returned to 'tower:-4"2vbyline.52.; -Forstripping purposes-incolumn 50, either stripping.` Y'steam, introduced at: 5 4; or bottoms reboilerq `1 j finoved -aslanloverheadv distillateatf; and; if desired, a' side-'stream' may beremoved at 31.. i," It'willbe appreciated-that` by. preventing; thereflux from the rectifying section -from` .mixing withthefeed I am ableto eiect a mateijialre Furthermore, because of the smaller I9, as thekquantity of light components in the' stripping section is substantiallylowered. Since.` Y

thereflux stream withdrawn in line 24 'is onlyj a small percentage ofthe feed to tower Ilif'anciY` contains .no very high boilingcomponents,the amount Yof stripping steamjor reboiling heat .refA Iquired vin stripperVV 26 is small.

age-of llight components in the Astripping section,

containing fewer decks, whereby `the Voverall ap.-

p'aratus costjis as low as, or lower than, thatiorr 'Y a; single columnwith-added. decks.'

It is, of course, to b eunderstood that the Asy afmodilication ofA myvprocess,fthec oxn'pclnments of the hydrocarbon mixture may begeerde- 1f rated by means of flashing.,`- In such' case,'1t h e ormsofl apparatusin 'Figs'.12-and 3 `may beemf; ployed.. `These vforms of apparatusare'especiallyl applicable when reboiling! ofrthe' bottoms from'.

ther applicablelwhemor any reason, the pres` enceloff steam. inthedistillation tower is found' ob'jectionz'iblelf f 1i f'. 1 When ahydrocarbon mixture is to be'subjectedv to Vthe Yflashing operation', I.prefer .totheatfrthe mixture toffa temperatureat wl'ii'chitV willbel.,somewhat overflashed, i 11n"r this manner I insure Vsubstantial'vaporizationl of all theA `light compo-.

nentsiin the mixture. However, ra considerableA portion of the heavycomponentswill also be .va-. porize'dz-with, or entrainedl by f.thelight :compos nenty vapors'.

It maybe said that, -n general, the greater the overnaslmthe better .theseparation obtained betweenjlight 'andgheavycomponents.` Howeverfy I themaximum improvemen1-;.obtainable is limited by the, mixingjof thevdowncmiingvoverilashed material with thelbottoms fhisr material, .as

previously mentioned,.oftenfcontains.a consider- A Y able Iamount oflight lcomponents 'which,mustbe f Y t restripped fromthe heavy.materialif allori/'edm'` mix .therewitl'lL This conditionisnotfimproved In .accordancefwith t all vvthefliglntj Vcomponen'tfs Y arevaporizedi 33ecauseof the'loverfla'shinkgna considerable Vaniorrit light'cbmponentswhich vare `stripped from. the

may be used;. y:

".fAslin theoperation' of the apparatusshqwn in Fig.. 1, .bottoms-,5sfrom towersu, being @di centzincharacter to bottoms` 5 81 irornfto we` 1f42 l l a residual VConsideraloly less'stripping 'e percen't-y .i

. Sep# x arate stripping column 25 may be incorporated inside tower II!as a stripping zone'separateffrorn l stripping setion I4, 'if itis'foundy desirable to. J1* ido Sofi" fr'le. .1 e' 'Y "e vformoiembodimentjot my invention: shoiwnfinFig. 2,f a suitably pre-11 77.heated hydrocarbon mixtur'eiisedtojflashingchamber' in distillationtowerlvl2. The mixtnre Y 1 is preferably overlashed sothatlsubtsan'tially I.

tion Y S44. Reiluxintroduced at 45 absorbs Ythese'lie'avy Y 'icomponents from 'the vaporfstrear'nf; 'I'h'ede'f--scending.refluxcontaining the'absorbed-heavycomponents isf collectedon'iplate Mtandpassed` throgli'line 38"to'js`tripping .column 50;; t Thel components-are removed at as" overhead dis-I tillate, andfjdesired; aside;` streaml maybe withdrawn at 6 If it is desired to use steam to orany other reasonl,lth'e presenceof `steamli'n flash distillation tower42or 1in fractionating column l!! is objectionable, the form ofembodistripvtnelnydrb-l carbon mixture, but, 'because ofcorrosivefefects any'retained light distillatecomponents fromtheunvaporized heavy residual` .componentsg-a mentshown in Figf3 maybeused. Steam is employed as the stripping'medium infcolu'mn. The jlightcomponents andsteam-Iare taken ofi' overhead at T, condensed incondenser 'lL-'and allowed to separate in settling tank' 14. Water isremoved at "l5 andthe lightcomponentsfree' of water, are`returned'bypump lthroughline 'I8 to tower`ll2. Inthis mannersteam is`preventedffrom entering tower 42. 's Y 4. V.

Use ofthereux stripper has a definite advantage, fespecially in.. theflashing -Toperatiom when. the residual.'product has lazboiling` rangevsuch as .to make it impracticable to reboil it atf a reasonabletemperature, asv isre'quiredinthe .substantial portion of the heavy-residual components 'beingvaporized with and entrained by the?resulting light distillate. component vapors, subjecting thelightdistillate component vapors to the action of'a reflux liquid forVthe'con-` densat'ion'A and absorption inthe reflux liquid of thevaporized and entrained heavy residual com-T ponents, withdrawing 'theentire reflux. liquid containing saidl condensed and'absorbedheavyresidual components and' some, light Adistillate components from saidYcolumn at `a point imme- Y diately above the point of feed withoutpermit" ting any'of said reflux` liquid tozcommingle with'. the' heavyunvaporized residual'- components in said column, separately-strippingsaid withdrawn refluxliquid inan independent stripping zone to separatethe lightfdistillate components` from the heavyresidual componentstherein,return ing the'stripped light distillatecomp'onentsto Y.Vsaidcolumn at apoint abovethe point offre'- ordinary scheme ofreboiling and Vstripping of Y bottoms'. The carrying `effect of thelightcomponents causes the feed temperature to'be lower.

than the -reboiling temperature A.would `ghe, `even when a `considerableamount of .overflashing is'` done. The overflashed material has .a:relatively low boiling range and may be` easily yreboiled inV the sidestripper. accomplish vthe separation lowertemperature. f

VAs an example o f the application of my-in vention, it was desired tofractionate a Reit# brook crudehaving a gravityV of .21:2.o A. P.

at a x considerably to obtain a' residue consistingfof r65% ofth'eAoriginal charge. AAnalysis-'ofithe crude in.di-.

catedrthat fthe desired residue ,hadvv an initial: Yflash point, atatmospheric;pressure;y in'excess of 800 F. Assume crackingwouldvoccurrat this temperature, reboiling of: the bottoms "could It is,Ytherefore, ,possible .to

flux withdrawal, removing from thefractionating columnkaboveY thepointof return of the stripped light distillate componentsall the lightdistillate Ycornponents including thoselight' dis# tillate componentswithdrawn .with` the entire reflux liquid tofthe stripping zone', `'saidremovedV light' distillate"-icomponents beingrfree of, the

`heavy residualr components, separately.` Vwith-- drawingthebottoms'from the fractionating co1- umn andfthe bottoms from thestripping zone,

approximatelylil" F., which temperature repre'- j sented abouta-38 to40% flash of the crude, and wasthen introduced into', flashY chamber.4010i Y theV apparatus shown in jlig. 2. @The flashed vapors containedsubstantially all tl'ie` lighticom; ponents in the crudeand-aporti'oniofithe heavierV conmonents as ;well. By collecting all of=.the 'l rfeiiuxat the bottom of4 theirectifying'section and separately Vstriprng this refiu'xfto remove the light .components therefrom, it waspossible' to obtainmthe desired residue'Y by combining the bottomsfromi'the reflux stripper with the bottoms from thedistill'ation towers;Y

While 1 haveshown andfdescribed preferred' forms of embodiment ofV myinvention, I am aware that other-modifications may be made thereto, andI, therefore, desire a broad interpretation of my invention within' thescope and spirit of the disclosure herein andthe claims appendedhereinafter.

Iclaim: l 1. In the method ofV sharply Yf ractionating ahydrocarbonmixture Vin a fractionating column to obtain` a bottomsfraction comprising 'a predetermined percentagerof said mixturevconsisting of all the heavy yresidual'components thereof,

and vjoinin'gf'fsagid bottoms streams Y having similar andoverlappingcharacteristics and 'jointly constitutingthe 'bottomsfraction comprising the predetermined. percentage of the mixture andconsistingf'substantially only ofzthe` heavy refsdual=fcemponents fofsaid mixture and being` free ofthe light distillate 'componentsthereof." 2. In'the method of sharply fractionatingla hydrocarbonmixtureffin Va fractionating column to obtain a bottomsfra'ctioncomprising apredetermined percentageV of said mixture, consist-4`ing'of-a'll the heavy residual 'components `th`ereof,` the stepsf which'comprise heating the hyf drooarbon mixture to a flash temperature higherthanf the corresponding distillation temperature 4off-,thepredetermined" separation, overflashing said heated mixtureinthefractionating column to separate substantially all the light distillatel, components therefrom'fa'substantial portion of the heavyres'idualcomponents being vaporized withand entrained `by the resulting lightdistillate component vapors. subjectinglthe vapors vto the actionof arefluxliquid for the condensa` tionV and ahso'rption'inthe refluxfliquidofthev vaporized` and ,entrained fheavy' residual com# penents,withdrawingtlie entire reflux' liquid comprising said condensed andabsorbed heavy 4residual components and some` light distillatecomponents from said column'at a point immediately'above the point offeed without permitthe steps which comprise heating the hydrocarbonmixture to a dash temperature correspondf ing to the distillationtemperature of the-predetermined 'separationg flashing the heatedVmixture in the frac'tionating'column to separate the greater portionofthe light distillate components from the heavy residualcomponents'stripping ting any of said reflux liquid to commingle withthe heavy unvaporized residual components in said column, separatelystripping ys'aid withdrawn reliux liquid in an independent'strippingzone to separate the light distillate components from the heavy residualcomponents therein, return'- ing the stripped light distillatecomponents to said column at a point above the point of refiuxwithdrawal, Yremoving from Vthe fractionating column above the point ofreturn ofthe stripped light distillate components Vall therlightdistillate 1 components including those light distillate,

components withdrawn with the entire reflux liquid toi-,thestrippingezone; saidlremyed-:lightt distillate.- compor-ients--being!-vfree.- ci'L the.. heavy.; residuali.: components, separately ewithdrawing; the bottoms-fromthe.frastionatingzcolumn. and: tneibottomsfrom` the.stripping.zolle;Y andioining-f saidifbottomssstreams;,hallinec similar: and;- over? lapping.. characteristics. .andl jointly,cfmstltutingl the -bottomsiraction .compelsing.-the.desiredfprerdeterminedfpereentaeefot-thesmixture. and-lconsisting substantially,onlyofathe-heavy residual.

components: of.. said mixture: andi. being free of..

the-,- light distillate. componentsnthereof.

, .35.; 111 thesmethodmof ,sharplyffractionatlng;a}` j hydrocarbon'mixture in; a -fracl'iionating Vcolumn obtain algbottoms fraction.comprising. afpre-.I

determined.' percentage: of: said.` mixtureV consiste..

ingfofl, all, the fheavynresidual ,components rthereof ,e Saidlmixtureialsoacon-taining- -componentsf corro,-

Siiiez ing the presence not.; steam, 'the steps which;`

@Qmpifise heating the f hydrocarbon? mixture.. to at.'

least fag Hasn-.temperature corresponding Atc theJ distillation.;temperature of.; the predeterminedV Sepelaliln lashinesaidheatedmixture.' in the. fractipnatingycolumn; in the absence!of; steam t0.: separate :substantially al1; 1 the.` light distillate. Ycornpgnents-therefrom;afsubstantial portion ofV thefheagy'residualvcomponents being vaporized viithyand ,enliraned bythef resulting lightdistillate C'Qmeenent: vapors; subjecting 'the vapors .to theaction 0ina V.lfeiill'x` liquid.- rfor the 'condensa-V loserption in thelreuz.liquidof the ping.- zone-'tof-separate the light'. distillate com`ponents. from. .theheavy-residualicomponents therein.- condensingthe-resultant light distillate @Qmppnent vapers and steam. and*separatingl the water. from -the condensed `light distillate com-1lponents -wherehytlle veffect of v`the corrosive coinypnn expatsisalocalized.;l returning l.the `.stripped light' dstill atei componentsto saidffcolurnn at a point above: the `pointl-lof; reflux.vnthdrawval-,v removing firomthefractionating:columnabove the point y @f.return offtheastrippedg'light distillate corn` Y ponentscallhtheelightYdistillate components inelueung ,tlneserllgne :distillate componentswithl diawn-:Witl'lfthef-entire reulxr'liquid to the strippin-,g1Zone,-saidremovedrlight distillate components b eing-y freefof the. heavyresidual vconlponentm y separately. withdrawing the bottoms and;entlaned heavyresidualcom- @3275535 I from the;fractionat.ineAcoluinnpandathe bottoms.

fromthe strippingzone-andi-jcining said streanul` the.' predeterminedpercentageci the original rifiniture.y and consisting-fsubstantiallyronly ofthe heavyaresidual.,components of. saidy mixture-and;

being free` of the light-gdistillate-A components; thereof; l

to. obtain a; bottoms-. fracticnf.comprising a predeterminedpercentage'ofrsaidfmixt'ure consisting; L olf-.alliv the .heavy residual=components thereof,; i

the'steps which comprise heating the hydrocar residual components #being.va'porized with Y and entrainedf. bythe-1r resulting light'fdistillateToom-J'.A

. ponent vapors, Vsubjecting thelight distillate' component? vapors to'.'the laction of'a reflux/Hq@ 25 uid'ior the: condensation `andabsorption'in 'the reux liquid 'ofthe Vaporized'land'f.entranedheavyresifdual components, withdrawing Athe en tigre reiluiliquid'containing s'aidcondensedrand absorbed heavy Yresidual' componentsand]somev 30,. light distillate components from said column-'atia..pointf immediately above thepointfclfffeed2 commingle with'the heavy.unvaporized residual components in said column, separately stripping`said. withdrawn .reiiluxfliqud lin an independent stripping zone toVseparate theli'gh't distillate lcomponents from theheavy residualcor'nponents"y if the? light distillate-` co'mponents'. including those"light ,distillate components 'withdrawn v'v'vith "the le entirereliure-.liquid tothe stripping zenegjsad removed light distillate'components being" free? `oit thevheavy residuali components,separatelif1 A withdrawingth'e bottoms from'the 'fractiona'tingf 7column and the 'bottomsiromthe stripping `zoneL 5,9. enajelnlngz saidbottoms-streams having similari predetermined percentage of7 the mixture'and- `free of thelight vdistillate components thereof;

PIERRE-LAMBERT;

to constitute Ythe bottoms fraction ,comprising-fr 4. inthe methodoffsharplyfraetlonanrig. a: hydroca.rbcn.y mix-turcen a: fractionatingcolumn:A 'f

bonfmixture vto at-leastaash temperature:core- :-4 respondingA to the-distillationztemperature of the. predetermined separation,` flashing.thefllieated f.. mixture in the `fractionatin'g columntons'eparate Ysubstantially all .the lightrdistillatefcomponentsf therefrom;a"substantial..portion2 ofithe heavy' without-permitting any ofseidienuxuiquld'te of the-stripped Alig-nl; distillate eempenentsellandi overlapping. characteristics 'and jointlyconj. stituting the,bottomslraction comprising they` consisting sl'ibstan'tiallyllonlyl`of` the heavyyre-- A sidual components'of 'said'imixture var.ldb'eing

